Aspiration monitoring system and method

ABSTRACT

In one embodiment, system for real time monitoring of catheter aspiration includes a housing having a first port adapted for connection to a vacuum source and a second port adapted for connection with an aspiration catheter, a pressure sensor in fluid communication with an interior of the housing, a measurement device coupled to the pressure sensor and configured for measuring deviations in fluid pressure, and a communication device coupled to the measurement device and configured to generate an alert signal when a deviation in fluid pressure measured by the measurement device exceeds a pre-set threshold. In another embodiment, the system for real time monitoring of catheter aspiration further includes a vacuum source for connection to the first port and an aspiration catheter having an aspiration lumen for connection to the second port.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This application is a continuation of U.S. Pat. App. No. 16/792,817,filed on Feb. 17, 2020, which is a continuation of U.S. Pat. App. No.15/866,414, filed on Jan. 9, 2018, now U.S. Pat. No. 10,603,415, whichis a continuation of U.S. Pat. App. No. 14/979,393, filed on Dec. 27,2015, now U.S. Pat. No. 9,895,473, which is a continuation of U.S. Pat.App. No. 14/678,282, filed on Apr. 3, 2015, now U.S. Pat. No. 9,248,221,which claims the benefit of priority to U.S. Provisional Application No.61/976,975, filed on Apr. 8, 2014, all of which are incorporated byreference in their entirety herein for all purposes. Priority is claimedpursuant to 35 U.S.C. § 120 and 35 U.S.C. § 119.

BACKGROUND OF THE INVENTION Field of the Invention

The field of the invention generally relates to an aspiration system forremoving, by aspiration, undesired matter such as a thrombus from afluid carrying cavity, duct, or lumen of the body, such as a bloodvessel.

Description of the Related Art

A treatment method for removing undesired matter such as thrombus from ablood vessel of a patient involves use of an aspiration catheter havingelongate shaft formed with an aspiration lumen extending therein. Anaspiration catheter may also include a guidewire lumen for placement ofa guidewire, which is used to guide the aspiration catheter to a targetsite in the body. By applying a vacuum (i.e. negative pressure) to aproximal end of the aspiration lumen, for example, with a syringe havinga hub that is connected to the proximal end of the aspiration catheter,the matter can be aspirated into an aspiration port at the distal end ofthe aspiration catheter, into the aspiration lumen, and thus be removedfrom the patient.

SUMMARY OF THE INVENTION

In one embodiment, a system for real time monitoring of catheteraspiration includes a vacuum source, an aspiration catheter having anaspiration lumen, a housing having a first port configured to couple tothe vacuum source and a second port configured to couple to theaspiration lumen of the aspiration catheter, a pressure sensor in fluidcommunication with an interior of the housing, a measurement devicecoupled to the pressure sensor and configured for measuring deviationsin fluid pressure, and a communication device coupled to the measurementdevice and configured to generate an alert when a deviation in fluidpressure measured by the measurement device exceeds a pre-set threshold.

In another embodiment, a system for real time monitoring of catheteraspiration includes a housing having a first port adapted for detachableconnection to a vacuum source and a second port adapted for detachableconnection with an aspiration catheter, a pressure sensor in fluidcommunication with an interior of the housing, a measurement devicecoupled to the pressure sensor and configured for measuring deviationsin fluid pressure, and a communication device coupled to the measurementdevice and configured to generate an alert signal when a deviation influid pressure measured by the measurement device exceeds a pre-setthreshold.

In another embodiment, a method for real time monitoring of catheteraspiration includes the steps of inserting an aspiration catheter havingan aspiration lumen into a patient, providing a system for real timemonitoring of catheter aspiration, the system including a housing havinga first port adapted for detachable connection to a vacuum source and asecond port adapted for detachable connection with the aspiration lumenof the aspiration catheter, a pressure sensor in fluid communicationwith an interior of the housing, a measurement device coupled to thepressure sensor and configured for measuring deviations in fluidpressure, and a communication device coupled to the measurement deviceand configured to generate an alert signal when a deviation in fluidpressure measured by the measurement device exceeds a pre-set threshold,coupling the first port to a vacuum source, coupling the second port tothe aspiration lumen of the aspiration catheter, and causing or allowinga body fluid to be aspirated through the aspiration lumen of theaspiration catheter, wherein the measurement device measures fluidpressure during aspiration of the body fluid, and wherein thecommunication device generates an alert signal when one or more measureddeviations in fluid pressure exceed a pre-set threshold during theaspiration of the body fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a system for aspiration according to anembodiment.

FIG. 2A is a view of an aspiration monitoring system according to afirst embodiment.

FIG. 2B is a view of an aspiration monitoring system according to asecond embodiment.

FIG. 3 is a view of an aspiration monitoring system according to a thirdembodiment.

FIG. 4A is a sectional view of an aspiration catheter in a blood vesselprior to contact with a thrombus.

FIG. 4B is a sectional view of an aspiration catheter in a blood vesselupon contact with a thrombus.

FIG. 4C is a sectional view of an aspiration catheter during a loss ofvacuum.

FIG. 4D is a sectional view of thrombi being aspirated through anaspiration catheter.

FIG. 5A is a graphic representation of pressure vs. time for thecondition of FIG. 4A.

FIG. 5B is a graphic representation of pressure vs. time for thecondition of FIG. 4B.

FIG. 5C is a graphic representation of pressure vs. time for thecondition of FIG. 4C.

FIG. 5D is a graphic representation of pressure vs. time for thecondition of FIG. 4D.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention relates to a monitoring, warning and communicationsystem for aspiration catheter systems. Clogging of aspirationcatheters, for example by large pieces of thrombus, is a common concernfor users. Techniques to avoid clogging/choking of material within thecatheter often involve rapidly, aggressively advancing the aspirationcatheter or gently plucking at edges of a thrombus to insure only smallpieces or portions are introduced at a time, pieces which are smallenough to not clog or occlude the aspiration lumen. When a devicebecomes clogged during use, the potential for inadvertent dislodgment ofthrombus downstream increases; this is referred to as distal embolism.As aspiration procedures of this type are often used in highly technicalemergent settings, early clog detection of the aspiration catheter forthe user during aspiration can contribute to the success of theprocedure and clinical outcome. Some sources have reported that up to50% of aspiration catheters used get clogged during use.

Additionally, the user may have difficulty determining whether there hasbeen a loss of vacuum in the system, for example because of the syringe(or other vacuum source) being full of fluid or because of a leak in thesystem. Blood is relatively opaque and can coat the wall of the syringe,thus making it difficult to determine when the syringe becomes full.This makes it difficult to determine whether sufficient vacuum is beingapplied to the aspiration catheter. It is also difficult to determinewhether there is an air leak in the system, which can be another causefor a loss of vacuum even before the syringe becomes full of theaspirated fluid.

During the aspiration of thrombus with an aspiration catheter, it isdifficult to identify when thrombus is actively being aspirated, andwhen only blood is being aspirated. Typically it is desired to notaspirate sizable quantities of normal blood from blood vessels, becauseof the importance of maintaining normal blood volume and blood pressure.However, when tracking the tip of an aspiration catheter in proximity toa thrombus, it is difficult to know whether the aspiration catheter hasactively engaged a thrombus, whether it has aspirated at least a portionof the thrombus, or whether it is not engaged with the thrombus, and isonly aspirating blood. The use of aspiration catheters can therefore beinefficient, and cause more blood removal than desired, causing a userto minimize the length of the therapy and in severe cases necessitatingblood transfusion. An increased volume of normal blood being aspiratedalso means that the vacuum source (e.g. syringe) will fill in a shorteramount of time, thus required more frequent replacement of the vacuumsource. Distal embolism may occur if the vacuum pressure is notsufficient, and yet the user is not aware.

An aspiration system 2 is illustrated in FIG. 1 and is configured toallow real time monitoring of catheter aspiration. The aspiration system2 comprises an aspiration catheter 4, a vacuum source 6, a valve 8,extension tubing 10, and an aspiration monitoring system 48 including anin-line pressure transducer 12. The aspiration catheter 4 has a proximalend 14 and a distal end 16 and an aspiration lumen 18 extending from theproximal end 14 to the distal end 16. The aspiration lumen 18 may besized for aspiration of thrombus, and in some embodiments may have aninner diameter of between about 0.38 millimeter (0.015 inches) and about2.54 millimeters (0.100 inches). The aspiration catheter 4 includes ahub 20 at its proximal end which may include a female luer connector 22.The aspiration lumen 18 at the distal end 16 of the aspiration catheter4 may include an angled orifice 24, which aids in the tracking throughtortuous or occluded vasculature. In some embodiments, a guidewire lumen26 is coupled to the distal end 16 of the aspiration catheter 4, and isconfigured to track over a guidewire 28. The vacuum source 6 maycomprise a syringe, and may be sized between 5 ml and 100 ml, or between20 ml and 60. The vacuum source 6 may comprise a VacLok® syringe, madeby Merit Medical, Salt Lake City, Utah. The vacuum source 6 may includea barrel 30 and plunger 32, with a lock 34 which is configured to retainthe plunger 32 in position in relation to the barrel 30, for example,when the plunger is pulled back in direction D to create a negativepressure (vacuum) inside the barrel 30. In some embodiments, the vacuumsource 6 may comprise any other type of evacuatable reservoir, or maycomprise a vacuum pump. The vacuum source 6 is connected to theaspiration lumen 18 of the aspiration catheter 4 via the extensiontubing 10 and the valve 8. In some embodiments, the vacuum source 6 maybe connected directly to the aspiration lumen 18 of the aspirationcatheter 4. Male luer connectors 36 and female luer connectors 38 areindicated in FIG. 1 . The valve 8 may be a standard two-way stopcock, asillustrated.

The pressure transducer 12 of the aspiration monitoring system 48 isconfigured to be fluidly coupled between the vacuum source 6and theaspiration catheter 4. In FIG. 2A, the aspiration monitoring system 48is illustrated as a self-contained device of a first embodiment. Thepressure transducer 12 comprises a housing 40 having a cavity 42extending between a first port 44 and a second port 46. In someembodiments, the first port 44 comprises a female luer and the secondport 46 comprises a male luer. In some embodiments, the first port 44comprises a female luer lock and the second port 46 comprises a maleluer lock, each of which is attachable to and detachable from acorresponding luer lock of the opposite gender. The first port 44 isconfigured to be coupled to the vacuum source 6, either directly, orwith the valve 8 and/or extension tubing 10 connected in between. Thesecond port 46 is configured to be coupled to the aspiration lumen 18 ofthe aspiration catheter 4, for example, by coupling the second port 46directly or indirectly to the hub 20 of the aspiration catheter 4. Whenthe aspiration system 2 is used to aspirate body fluids and/ormaterials, for example blood and/or thrombus, the body fluids and/ormaterials are aspirated through the aspiration lumen 18 of theaspiration catheter from the angled orifice 24 at the distal end 16 tothe female luer connector 22 at the proximal end 14, then pass throughthe second port 46 of the pressure transducer 12 first, through thecavity 42, and then through the first port 44. Depending on the amountof amount of vacuum (negative pressure) applied by the vacuum source 6,and the amount of flow resistance and resulting pressure drop along theaspiration system 2, the pressure within the cavity 42 will vary. Forexample, a more viscous fluid like blood, or a fluid having solid,semi-solid, or gel-like particles or portions, will cause more flowresistance through the relatively small aspiration lumen 18 of theaspiration catheter 4 than would water or normal saline solution. Thusthe pressure within the cavity 42 of the pressure transducer 12 willdecrease (the amount of vacuum will increase) as the flow resistance inthe aspiration lumen 18 increases.

For definition purposes, when speaking of the amount of vacuum, apressure of, for example, -15,000 pascal (-2.18 pounds per square inch,or psi) is a “larger vacuum” than -10,000 pascal (-1.45 psi).Additionally, -15,000 pascal is a “lower pressure” than -10,000 pascal.Furthermore, -15,000 pascal has a larger “absolute vacuum pressure” thandoes -10,000 pascal, because the absolute value of -15,000 is largerthan the absolute value of -10,000. In FIG. 2A, a vacuum sensor 50 isdisposed within the cavity 42 of the housing 40 and is in fluidcommunication with fluid that passes through the cavity 42. The vacuumsensor 50 may be a standard pressure sensor or transducer, including apressure sensor designed primarily for measuring positive pressure. Itmay use any type of pressure sensing technology known in the art,including MEMS Technology. In some embodiments, the vacuum sensor 50 isconfigured for highest accuracy and/or precision within the range ofpressures between about 0 pascal to about -101,325 pascal (-14.70 psi),or between about -45,000 pascal (-6.53 psi) and about -90,000 pascal(-13.05 psi), or between about -83,737 pascal (-12 psi) and about-96,527 pascal (-14 psi). In some embodiments, the power requirement forthe vacuum sensor may range from 2.5 volts DC to 10 volts DC. In someembodiments, the vacuum sensor 50 may be an analog gauge with an outputvoltage. In the self-contained embodiment of the FIG. 2A, the vacuumsensor 50 is powered by one or more battery 52. Based on the powerrequirements of the vacuum sensor 50, and the power requirements ofother components of the aspiration monitoring system 48 describedherein, in some embodiments the one or more battery 52 may range between1.5 volts and nine volts. Also contained within the housing is ameasurement device 54, which in some embodiments may comprise amicroprocessor. The measurement device 54 is coupled to the vacuumsensor 50 and receives signals from the vacuum sensor 50 indicative ofreal time measured pressure. In some embodiments, the measurement device54 includes a memory module 56 in which information is stored that maybe used by the measurement device 54, for example, in calculations.

One or more communication devices 58 a, 58 b, 58 c are included withinthe aspiration monitoring system 48 and are coupled to the measurementdevice 54. Each of the one or more communication devices 58 a-c areconfigured to generate a type of alert comprising an alert signal 60a-c, in response at least in part to activity and output of themeasurement device 54. In some embodiments, the communication device 58a may include one or more LEDs (light emitting diodes) configured togenerate a visible alert via a visible alert signal 60 a, such as lightthat is continuously illuminated, or is illuminated in a blinkingpattern. In some embodiments, lights other than LEDs may be used. Insome embodiments, the communication device 58 b may include one or morevibration generators configured to generate a tactile alert via atactile alert signal 60 b, which may include, but is not limited to,vibration or heat. In some embodiments, the vibration generator maycomprise a piezoelectric device which is configured to vibrate when avoltage is applied. In some embodiments, the communication device 58 cmay include one or more sound generating devices configured to generatean audible alert via an audible alert signal 60 c, such as a continuousnoise, or a repeating noise. In some embodiments, the sound generatingdevice may comprise a buzzer which is configured to sound one or moreaudible pitches when a voltage is applied. In some embodiments apiezoelectric device, such as that described in relation to thecommunication device 58 b may also serve as a sound generating device,included as communication device 58 c.

A user of an aspiration system 2 may desire to be notified of severalconditions which may occur during use of the aspiration system 2. Thesepotential conditions include, but are not limited to clogging, a loss ofvacuum due to filling of the vacuum source 6 and or a breach, break orpuncture in the aspiration system 2, and the engagement or aspiration ofnon-fluid, solid or semi-solid material such as thrombus. The aspirationmonitoring system 48 of FIG. 2A is configured to alert users of anaspiration system 2 about real time status of the aspiration system 2,including operational conditions, which include: whether vacuum is beingapplied or not; flow conditions, which include whether a thrombus isengaged, whether a thrombus is being actively aspirated, whether thesystem is leaking air, whether the system is clogged, whether the vacuumsource 6 is full and/or needs to be changed; or other potential set upissues. The real time feedback provided frees a user or operator fromthe need of excessive personal monitoring of the vacuum source 6,extension tubing 10, or other portions of the aspiration system 2, forimproper or undesired flow or operation conditions, and thus allows theuser to focus more attention on the patient being treated.

The pressure transducer 12 of the aspiration monitoring system 48 isconfigured to continuously measure and monitor the absolute pressureamplitude within the closed system of the aspiration system 2, and alsois configured to measure and monitor the relative pressure over time todetect noteworthy flow changes within the flow circuit of the aspirationsystem 2. Some changes are discernible via absolute pressuremeasurement, while more subtle pressure deflections may be compared to astored library in memory. Noteworthy conditions may be signaled to theuser when appropriate. In some embodiments, the unfiltered signal may beamplified by an amplifier and filtered by a filter, for example, toincrease the signal-to-noise ratio. Examples of the (background) noise57 in an unfiltered signal can be seen in FIGS. 5A-5D (labeled in FIG.5A). In some embodiments, one or more algorithms may be used, asdescribed herein, to identify particular conditions of interest.

FIG. 2B illustrates a second embodiment of an aspiration monitoringsystem 62 having a pressure transducer 12 having a vacuum sensor 50disposed within the cavity 42 of a housing 40. The vacuum sensor 50 maybe powered by at least one battery 52. In some embodiments, the pressuretransducer 12 may be reusable, and may be configured to allow chargingof the battery 52, or of a capacitor (not shown) by direct chargingmethods, or by inductive power transfer methods and devices known in theart. Unlike the aspiration monitoring system 48 of FIG. 2A, theaspiration monitoring system 62 of FIG. 2B comprises a measurementdevice 64, memory module 66, and communication device 68 which areexternal to the pressure transducer 12. A power module 72, alsoexternal, may be used to power any of the measurement device 64, memorymodule 66, or communication device 68. The communication device 68 maybe any of the communication device 58 a, 58 b, 58 c described inrelation to the aspiration monitoring system 48 of FIG. 2A, and areconfigured to product an alert via an alert signal 70. The communicationdevice 68 may be portable so that it may be positioned close to theuser.

In some embodiments, the communication device 68 may be wearable by theuser. FIG. 3 illustrates an aspiration monitoring system 78 whichincludes an antenna 80 coupled to a measurement device 76. Themeasurement device 76 is similar to the measurement device 54 of priorembodiments, except that it wirelessly sends a communication signal 84via the antenna 80 to a corresponding antenna 82 of a communicationdevice 74. In some embodiments, the communication device 74 comprises awristband which the user wears, and which may include a vibrationgenerator or heat generator. In some embodiments, the communicationdevice 74 comprises an audio speaker which may be attached to equipmentor even to the patient or user. In some embodiments, the communicationdevice 74 comprises an audio speaker on an earpiece or earbud that theuser may wear. In some embodiments, Bluetooth® communication technologymay be used.

FIG. 4A illustrates the distal end 16 of an aspiration catheter 4 withina blood vessel 86 having at least one thrombus 88. The aspirationcatheter 4 is being advanced in a forward direction F, but the distalend 16 of the aspiration catheter 4 has not yet reached the proximalextremity 94 of the thrombus 88. A vacuum source 6 (FIG. 1 ) has beencoupled to the aspiration lumen 18 of the aspiration catheter 4 andactivated (i.e. the valve 8 is open) causing blood 96 to be aspiratedinto the aspiration lumen 18 (arrows A). Turning to FIG. 5A, acorresponding curve 98 is represented for the normal fluid (e.g. blood)vacuum over time for the condition of FIG. 4A. The curve 98 representsvacuum pressure over time sensed by the vacuum sensor 50 of any of theembodiments presented. No leaks are present and no thrombus is beingevacuated, and therefore the curve 98 includes a downward slope 99 whenthe vacuum source 6 increases the vacuum up (lowers the pressure) withinthe cavity 42 of the pressure transducer 12 to a relatively steadystate. The steady pressure curve 97 continues while blood 96 is beingaspirated. As the vacuum is decoupled from the aspiration lumen 18, forexample by closing the valve 8 or by detaching any two of the ports(e.g. luers), or if the vacuum source 6 fills completely with blood 96,then an upward slope 95 is measured.

The measurement device 54, 64 is configured to compare the curve 97 withinformation stored in the memory module 56, 66 to identify thiscondition. In some embodiments, the measurement device 54, 64 uses analgorithm to make the comparison. In some embodiments, the measurementdevice 54, 64 then sends a signal to the communication device 58 a-c,74, and the communication device 58 a-c, 74 generates an appropriatealert. Communication device 58 a, for example a particular color LED,may be illuminated, or an LED may flash in a particular pattern ornumber of flashes. Communication device 58 b may create a characteristicsound, or may generate an audio message in a number of languages. Forexample, the audio message may state, “Thrombus encountered,” or “Nothrombus encountered.” Communication device 58 c may vibrate or heat ina characteristic pattern, for example, a certain number of repetitionsor a certain frequency between repetitions. The user may determine thatan additional fluoroscopic image (e.g. angiography) or other imagingmodalities may be necessary to better identify the location of thethrombus 88.

FIG. 4B illustrates the distal end 16 of an aspiration catheter 4advanced to a position such that the distal end 16 of the aspirationcatheter 4 contacts the proximal extremity 94 of the thrombus 88. Thecorresponding curve 93 in FIG. 5B represents vacuum pressure over timesensed by the vacuum sensor 50 of any of the embodiments presented. Thecurve 93 initially has a downward slope 99 followed by a steady pressurecurve 97, as in the condition of FIG. 4A, graphed in FIG. 5A, however,when the distal end 16 of the aspiration catheter 4 contacts theproximal extremity 94 of the thrombus 88, if the aspiration causes aportion of the thrombus 88 (for example a large or relatively hardportion) to enter and become trapped in the aspiration lumen 18, then aclog condition occurs. A similar condition occurs if the distal end 16of the aspiration catheter 4 is caught on the thrombus 88 by the vacuum,with virtually nothing flowing through the aspiration lumen 18. Ineither condition, the curve 93 includes a deviation (or disturbance) influid pressure 91. If the clog (or stuck condition) continues, then aflat, depressed pressure 89 is measured.

The measurement device 54, 64 is configured to compare the curve 93 withinformation stored in the memory module 56, 66 to identify thiscondition. In some embodiments, the measurement device 54, 64 uses analgorithm to make the comparison. In some embodiments, a pre-setpressure differential ΔP₁ may be stored in the memory module 56, 66 as athreshold, whereby the measurement of a pressure difference 81 less thanthis threshold does not result in the measurement device 54, 64commanding the communication device 58 a-c, 74 to send an alert signal60 a-c, 70. In some embodiments, when the pressure difference 81 isgreater than (or greater than or equal to) the pre-set pressuredifferential ΔP₁, the measurement device 54, 64 then sends a signal tothe communication device 58 a-c, 74, and the communication device 58a-c, 74 generates an appropriate alert. Communication device 58 a, forexample a particular color LED, may be illuminated, or an LED may flashin a particular pattern or number of flashes. Communication device 58 bmay create a characteristic sound, or may generate an audio message in anumber of languages. For example, the audio message may state, “ClogCondition.” Communication device 58 c may vibrate or heat in acharacteristic pattern, for example, a certain number of repetitions ora certain frequency between repetitions. When the user realizes that theclog condition is present, the user may pull on the aspiration catheter4 and readvance it, in an attempt to contact a portion of the thrombus88 that can be aspirated. If a portion of the thrombus is clogged in theaspiration lumen 18, and repositioning of the aspiration catheter 4 doesnot produce good results, the aspiration catheter 4 can be removed andthe aspiration system 2 can be repurged, for example by a positivepressurization.

FIG. 4C illustrates the distal end 16 of the aspiration catheter 4 in ageneral situation during which a breach in the aspiration system 2 hasoccurred. For example, a break, leak, puncture, pinhole, loosening, ordisconnection may cause air to be pulled into the aspiration lumen 18 ofthe aspiration catheter 4, the cavity 42 of the pressure transducer 12,of the interior of the extension tubing 10, valve 8, or vacuum source 6.As graphed in the curve 85 of FIG. 5C, a downward slope 99 and asubsequent steady pressure curve 97 are measured, but at the point intime of the breach 87 an upward slope 83 begins.

The measurement device 54, 64 is configured to compare the curve 85 withinformation stored in the memory module 56, 66 to identify thiscondition. In some embodiments, the measurement device 54, 64 uses analgorithm to make the comparison. In some embodiments, the measurementdevice 54, 64 then sends a signal to the communication device 58 a-c,74, and the communication device 58 a-c, 74 generates an appropriatealert. Communication device 58 a, for example a particular color LED,may be illuminated, or an LED may flash in a particular pattern ornumber of flashes. Communication device 58 b may create a characteristicsound, or may generate an audio message in a number of languages. Forexample, the audio message may state, “System Leak.” Communicationdevice 58 c may vibrate or heat in a characteristic pattern, forexample, a certain number of repetitions or a certain frequency betweenrepetitions. Upon receiving the alert, the user will check thecomponents of the aspiration system 2 and either fix the breach orreplace one or more of the components of the aspiration system 2. Forexample, in some cases, the communication device 58 a-c, 74 may alertthe user when the measurement device 54, 64 confirms a loss of vacuum,allowing the user to change or recharge the vacuum source 6, which hasbecome depleted (e.g. by filling with blood and/or thrombus).

FIG. 4D illustrates the distal end 16 of the aspiration catheter 4during the successful aspiration of pieces or portions 90 of thethrombus 88. In some cases, the pieces or portions 90 may follow atortuous path 92, due to disturbances or collisions with the inner wallof the aspiration lumen 18 while being pulled through the aspirationlumen 18. In some cases, the pieces or portions 90 may catch and slipwithin the inner wall of the aspiration lumen 18, for example, do tovariance of the inner diameter of the aspiration lumen 18 along thelength. Either of these situations can cause a corresponding series ofincreases and decreases in the pressure being sensed by the pressuretransducer 12, while the pieces or portions 90 are traveling through theaspiration lumen 18. As graphed in the curve 79 of FIG. 5D, a downwardslope 99 and a subsequent steady pressure curve 97 are measured, but asthe pieces or portions 90 of thrombus 88 travel down the aspirationlumen 18 of the aspiration catheter 4, a deviation 77 of fluid pressurecomprising a plurality of decreases and increases in pressure (increasesand decreases in vacuum pressure) is measured. As the pieces or portions90 of thrombus 88 exit the proximal end of the aspiration lumen 18 ofthe aspiration catheter 4, a second steady pressure curve 75 ismeasured. The duration 67 of the deviation 77 is the amount of transitof the particular significant pieces or portions 90 of thrombus 88. Theduration 67 can range quite a bit, but in some cases may be less than asecond or up to about 30 seconds. When again additional pieces orportions 90 of thrombus 88 are aspirated into and travel down theaspiration lumen 18 of the aspiration catheter 4, another deviation 73of fluid pressure comprising a plurality of decreases and increases inpressure (increases and decreases in vacuum pressure) is measured. Atthe end of the curve 79, the vacuum source 6 is shown filling completelywith blood 96 and the pieces or portions 90 of thrombus 88, and so anupward slope 95 is measured.

The measurement device 54, 64 is configured to compare the curve 79 withinformation stored in the memory module 56, 66 to identify when thepieces or portions 90 of thrombus 88 are actively being aspirated, as indeviation 77 and deviation 73, and when the pieces or portions ofthrombus 88 are not being actively, or substantially, aspirated, as insteady pressure curve 97, the steady pressure curve 75, and the steadypressure curve 71. In some embodiments, the measurement device 54, 64uses an algorithm to make the comparison. In some embodiments, a pre-setpressure differential ΔP₂ may be stored in the memory module 56, 66 as athreshold, whereby the measurement of a pressure difference 69 less thanthis threshold does not result in the measurement device 54, 64commanding the communication device 58 a-c, 74 to send a first type ofalert via an alert signal 60 a-c, 70. In some embodiments, when thepressure difference 69 is greater than (or greater than or equal to) thepre-set pressure differential ΔP₂, the measurement device 54, 64 thensends a signal to the communication device 58 a-c, 74, and thecommunication device 58 a-c, 74 generates an appropriate alert.Communication device 58 a, for example a particular color LED, may beilluminated, or an LED may flash in a particular pattern or number offlashes. In some embodiments, the communication device 58 a may comprisea light whose intensity increases proportionally with the pressure.Communication device 58 b may create a characteristic sound, or maygenerate an audio message in a number of languages. For example, theaudio message may state, “Thrombus being aspirated.” In someembodiments, communication device 58 b may comprise one or more noisesor beeps. In some embodiments, the communication device 58 b maycomprise a particular series of beeps corresponding to each differentcondition. For example, three short beeps may correspond to no thrombusbeing aspirated, while five long, loud beeps may correspond to a systemleak. In some embodiments, a plurality of different tones (pitches) maybe used to alert a user about different conditions. As an example, a lowpitch sound may be used for a first condition (e.g. no thrombus beingaspirated) and a second, higher pitch sound may be used for a secondcondition (e.g. a system leak). In some embodiments, a plurality ofdifferent tones may be used to alert a user about a first condition anda second plurality (e.g. in a different combination, or with additionaltones) may be used to alert a user about a second condition.Communication device 58 c may vibrate or heat in a characteristicpattern, for example, a certain number of repetitions or a certainfrequency between repetitions. When the user realizes that the thrombusis being aspirated, the user may choose to advance (or retract) theaspiration catheter 4, for example with fluoroscopic visualization,along the length of the thrombus 88, in an attempt to continue theaspiration of the thrombus 88. In some cases, the user may choose tostop the advancement or retraction of the aspiration catheter 4 at acertain amount of time after the alert is generated, in order to allowthe pieces or portions 90 of thrombus 88 to completely exit theaspiration lumen 18. When the measurement device 54, 64 identifies asubsequent steady pressure curve 75, 71 that follows a deviation 77, 73,the measurement device 54, 64 in some embodiments sends a signal thatcauses the communication device 58 a-c, 74 to generate a second type ofalert via an alert signal 60 a-c, 70. For example, in some embodiments,communication device 58 b may send an audio message that states,“Thrombus no longer being aspirated.” When the user realizes that thethrombus is no longer being aspirated, the user may advance or retractthe aspiration catheter, in an attempt to contact another portion of thethrombus 88 that can be aspirated. In some embodiments, the deviation 77may be positively identified as a true deviation indicating thrombusbeing actively aspirated, pressure difference 69 is between about 700pascal and about 1700 pascal. In some embodiments, the deviation 77 maybe positively identified as a true deviation indicating thrombus beingactively aspirated, pressure difference 69 is between about 1000 pascaland about 1300 pascal. In some embodiments, the deviation 77 may bepositively identified as a true deviation indicating thrombus beingactively aspirated, pressure difference 69 is about 1138 pascal. Thepressure difference 69 may be measured by determining a baselinepressure 63 and a peak pressure 61 and determining the absolute valuedifference. For example:

$\begin{array}{l}{\text{Absolute}\mspace{6mu}\text{value}\mspace{6mu}\text{difference}\mspace{6mu}\text{(AVD)}\mspace{6mu}\text{=}\mspace{6mu}} \\{\left| {\left( {- 89,631\mspace{6mu}\text{pascal}} \right) - \mspace{6mu}\left( {- 90,769\mspace{6mu}\text{pascal}} \right)} \right| = 1138\mspace{6mu}\text{pascal}}\end{array}$

Or for example:

$\begin{array}{l}{\text{Absolute}\mspace{6mu}\text{value}\mspace{6mu}\text{difference}\mspace{6mu}\text{(AVD)}\mspace{6mu}\text{=}\mspace{6mu}} \\{\left| {\left( {- 43,710\mspace{6mu}\text{pascal}} \right) - \mspace{6mu}\left( {- 45,102\mspace{6mu}\text{pascal}} \right)} \right| = 1281\mspace{6mu}\text{pascal}}\end{array}$

The pressure difference 81 (FIG. 5B) may also represent a deviation thatmay be identified in a similar manner, after which the communicationdevice 58 a-c, 74 generates an appropriate alert, such as, “Clogcondition.”

Because vacuum pressure is a negative pressure, the peak pressure 61, asshown in FIG. 5D, is actually a lower number than the baseline pressure63. In some embodiments, the measurement device 54, 64 may also beconfigured to make a comparison, for example by using an algorithm,between a stored differential time t₁ and a duration 65 of a single oneof the plurality of decreases and increases in pressure in the deviation77. For example, in some embodiments, the deviation may be positivelyidentified as a true deviation indicating thrombus being activelyaspirated, if the duration is between about 0.001 seconds and about 0.50seconds. In some embodiments, the deviation may be positively identifiedas a true deviation indicating thrombus being actively aspirated, if theduration is between about 0.005 seconds and about 0.10 seconds. In someembodiments, the deviation may be positively identified as a truedeviation indicating thrombus being actively aspirated if the durationis between about 0.05 seconds and about 0.20 seconds. In someembodiments, the measurement device 54, 64 is configured to recognizedeviation 77 after two or more decreases and increases in pressure aremeasured. In some embodiments, the measurement device 54, 64 isconfigured to recognize deviation 77 after five or more decreases andincreases in pressure are measured. In some embodiments, the measurementdevice 54, 64 is configured to recognize deviation 77 after ten or moredecreases and increases in pressure are measured.

Insertion of the pressure transducer 12 in line in either the embodimentof FIG. 2A or the embodiment of FIG. 2B does not measurably changeperformance characteristics of the aspiration system 2, because thecavity 42 is relatively short and has a relatively large inner diameter,and thus is not a significant source of fluid flow resistance. In someembodiments, the inner diameter may be between about 2.2 mm (0.086inches) and about 3.2 mm (0.125 inches). In some embodiments, themeasurement device 54, 64, 76 need not include a microprocessor, aspre-defined set points (e.g. for certain thresholds) may be included infirmware, microcontroller, or other locations. In some embodiments,including but not limited to the embodiment of FIG. 2B, the pressuretransducer 12 may be an off-the-shelf blood pressure monitor system,which is modified or augmented with other components. In someembodiments an off-the-shelf blood pressure monitor system may be usedas the output of the aspiration monitoring system 48, 62, 78. In someembodiments, an aspiration catheter 4 may have a pressure transducer inthe distal end 16. This pressure transducer may be used as the pressuretransducer 12 of the aspiration monitoring system 48, 62, 78. In someembodiments, a pressure sensor may be located within a Tuohy-Borstvalve, and introducer sheath, a guiding catheter, or another componentof the system through which is in fluid communication with theaspiration lumen 18. In some embodiments, the pressure sensor may belocated anywhere within the aspiration lumen of the aspiration catheter.

In some embodiments, instead of an LED, the visual alert is provided bya communication device 58 a comprising a display which displays visualmessages of text in a particular language, for example, “Thrombusencountered,” “No thrombus encountered,” “Clog condition,” “Systemleak,” “Loss of vacuum,” “Thrombus being aspirated,” or “Thrombus nolonger being aspirated.” The visual messages may be combined with any ofthe other alert signals 60 a-c, 70 described herein. The aspirationmonitoring system 48, 62, 78 described herein give real time awarenessto users performing aspiration procedures, such as the removal ofthrombus via an aspiration system 2. One skilled in the art willrecognize that by knowing the real time condition of the aspirationsystem 2, the user is able to immediately make changes to the procedurein order to optimize results, increase safety for the patient and/ormedical personnel, reduce costs (e.g. number of vacuum sources 6required), and reduce procedure time (also a cost benefit). Because theuser is typically performing multiple tasks during an aspirationprocedure, the sensory aid provided by the aspiration monitoring system48, 62, 78 allows the user to focus on these tasks without having tocontinually attempt to monitor conditions which are often difficult tovisually monitor. The user may also modify and control the aspirationmonitoring system 48, 62, 78 via an input 59 (FIG. 2B), which maycomprise a data entry module, keyboard, or a series of buttons with adisplay. The input 59 may in some embodiments comprise an auditory inputwhich accepts voice commands. Alternatively, the user may inputinformation and control the aspiration monitoring system, 48, 62, 78remotely. Some of the alerts which the user may select or deselect inthe aspiration monitoring system 48, 62, 78 include, but are not limitedto: whether the aspiration system 2 is potentially blocked or clogged,or is flowing normally; whether thrombus has been contacted or not;whether a clog has occurred; whether the vacuum source 6 is adequate, orwhether it has been depleted and requires replacement; whether there isa leak in the aspiration system 2; whether setup or connection of thecomponents of the aspiration system 2 was done correctly or incorrectly;whether to advance the catheter distally; whether to retract thecatheter; whether to continue moving the catheter at the same speed;whether to increase or decrease the speed of catheter advancement;whether thrombus is actively being aspirated; and whether thrombus stopsbeing actively aspirated.

In some embodiments, alternate power sources may be used, for example,standard AC power with or without an AC/DC convertor; direct connectionto existing equipment (e.g. vacuum pumps, etc.); solar power. Theaspiration monitoring system 48, 62, 78 may be packaged sterile or maybe resterilizable by techniques known by those skilled in the art. Insome embodiments, flow or volume gauges may be used in conjunction withor instead of the pressure gauge 12, in order to determine, for example,a clog, or a change in the amount of vacuum.

Though aspiration of thrombus has been described in detail, theaspiration monitoring system 48, 62, 78 has utility in any aspirationapplication wherein heterogeneous media is being aspirated. This mayinclude the aspiration of emboli (including not thrombotic emboli) fromducts, vessels, or cavities of the body, or even from solid orsemi-solid portions of the body, including, but not limited to, portionsof fat, breasts, and cancerous tissue.

In some embodiments, the aspiration system 2 is be provided to the useras a kit with all or several of the components described, while in otherembodiments, only the aspiration monitoring system 48 is provided.Though discussion herein includes embodiments for aspiration of thrombusand blood, the definition of the word “fluid” should be understoodthroughout to comprise liquids and gases.

In some embodiments, an additional or alternate sensor may be used tomonitor flow conditions for the notification of the user, including, butnot limited to: a Doppler sensor, an infrared sensor, or a laser flowdetection device. In some embodiments, an externally-attached Dopplersensor may be employed. In some embodiments, an infrared sensor or alaser flow detection device may be employed around the extension tubing10.

What is claimed is:
 1. A monitoring device for real time monitoring ofcatheter aspiration, comprising: a housing; an elongate passageextending within the housing and terminating in an orifice configured tobe coupled to a vacuum source, the passage configured to by coupled toan aspiration lumen of an aspiration catheter such that aspirated bloodcan transit through the passage and out the orifice; a pressure sensorcarried by the housing and configured to measure pressure within thepassage; a microprocessor coupled to the pressure sensor and configuredfor measuring deviations in the measured pressure; and a light coupledto the microprocessor and configured to generate a visual signal as aresult of a determination by the microprocessor that a change in themeasured pressure conforms with a particular relationship in comparisonto a pre-set threshold.
 2. A method for real time monitoring of catheteraspiration that utilizes the monitoring device of claim 1.